Several power and effective synthetic insecticides have been used to protect food and fiber crops with varied success for many years now. More recently, there has been a great deal of controversy about the effect of these on the environment and some of the insecticides which have been in extensive use have been banned. It is likely that other insecticides could be banned but which are still in use are considered to be potentially harmful to the environment but are required to be used for lack of other alternatives.
As a result, a search has been going on for "botanical pesticides" which are environmentally friendly. These are compositions which would deter insects or other pests but would have no or minimal harmful effect on the environment, particularly to humans who sometimes are at the end of the food chain and may thus suffer bio-accumulation.
Presently an agent known to protect crops from pests is Azadirachtin which is a natural product found in the seeds of the neem tree (Azadirachtin indica A. Juss). This has gained a lot of importance all over the world as the most environmentally safe pesticide. The neem tree is found in great abundance in India and also is distributed in other countries like Pakistan, Bangladesh, Burma, Thailand and Malaysia and is also found in Africa.
Several Azadirachtin isomers, derivatives and related compounds have been studied. From such studies it is evident that Azadirachtin A is the most important compound which has the desired insecticidal property. Azadirachtin A has been extracted from neem seeds and is found to have an anti-feedant property (which deters insects from feeding on plants) and growth regulation potency against such pests. It is readily applied by coating seeds or by applying a spray to the crops themselves.
Various methods of extracting Azadirachtin or such similar principles have been described in Indian patents 153415, 172150, 173327, 173328, 173449, 173989, 173996, 173997 and 173998 and U.S. Pat. Nos. 4,556,562, 5,391,779, 5,372,817, 5,352,677, 5,298,251, 5,281,618, 5,229,007 and 5,124,349. Azadirachtin is a known agent, but stable Azadirachtin A has not been purified to a higher content through a process which enriches the content to about 60-75% of the total Azadirachtin content without the use of laborious columns. The commercial uses of Azadirachtin A have been based on its stability and purification and nowhere in the above patents is a process for purifying and enriching Azadirachtin A described.
U.S. Pat. No. 5,736,145, upon which the present application relies for its teaching of a successful method of extracting Azadirachtin A from neem seeds is incorporated herein by reference.